1. Field of the Invention
This invention involves an assembly including at least one chip with one or more embedded magnetic heads.
It can be applied in particular to making helicoid recording heads for magnetic tape, for example amateur or professional video recording (home VDRs or camcorders) or also for computer data recorders which use tapes or disks. There could also be other applications for other types of recording heads (linear on tape, on cards, etc.).
The high frequencies which are possible due to the small size of the magnetic heads integrated in thin layers allow for digital recording (for example with the DVC norm for video or DDS for data recording). Tape data recording systems are for mass data storage with the highest capacities and at the lowest cost. Its computer applications are archiving of data and backups of hard disks of systems or networks for distribution of large programs or databases.
2. State of the Art
FIGS. 1 to 3 illustrate the structure of a magnetic head integrated in thin layers which is known from document FR-A-2 747 226. As illustrated in FIG. 1, the head includes two polar pieces 101, 102 separated by a head gap 14, two magnetic branches 161, 162 which partly cover the polar pieces, and a magnetic piece for flux closure 18. This set of pieces constitutes a magnetic circuit. Around the branches 161, 162 there are conducting windings 201, 202 for reading and/or writing of the information written and/or read on the recording medium (not shown).
FIG. 2 shows the complete head with two conducting strips 221, 222 allowing for access to the conducting windings 201, 202 and two electrical connection studs 241, 242.
The head shown in FIGS. 1 and 2 can be made collectively using micro-electronics techniques. To obtain a chip with one or several magnetic heads from a card which includes several components or chips, the components must be separated from each other and then the front part of the components next to the polar pieces 101, 102 must be machined to give them the rounded shape needed for proper functioning of the head. In FIG. 2, the rounded profile is schematically represented by the line 26.
FIG. 3 schematically shows a section view of a head along a line AA which goes through one of the conducting strips and one of the branches of the magnetic circuit as well as the head support. This figure shows a substrate 30, silicon for example, with one of the polar pieces 101 or 102, a magnetic branch 161 or 162, a conducting strip 221 or 222, and the electrical connection studs 241, 242. This unit is covered by a superstrate 40, in silicon for example. At the front of the head, the surface 26, called the bearing surface, has an appropriately rounded shape and a height h which is reduced with respect to the total thickness of the unit. At the back, the superstrate 40 is disengaged to leave the electrical connection studs 241, 242 exposed.
The chip (or chips) is mounted on a base 45, made of brass for example, on one of the sides of which there is a rigid printed circuit 46 which is electrically linked to the chip by stranded wires 481, 482. The printed circuit 46 links the head to the electronic circuits which control writing and/or reading.
The current chips for helicoidal recording are mounted on and glued to their bases. This gluing is done on the reference plane of the base, machined to give it good evenness, so that the head is perfectly parallel to the reference plane of the drum to which the base will be screwed. The position can be adjusted with the screw.
The current assemblies are poorly adapted to miniaturisation of heads, because the mechanical resistance of the chip on a single gluing side of the base is not sufficient when the size of the head becomes very small. In the future, integrated heads will progressively replace micro-machined heads, because they are much better suited to increasing the density of information. The heads will thus be smaller and smaller. The base must be adapted as a consequence. Gluing the chip to a single plane is not sufficient because it does not ensure good mechanical resistance of the head when it is working.
The Japanese patent application 60-020311 describes a support-magnetic head assembly in which a chip is introduced in a groove made at the front of the base.
Japanese patent application 07-296325 describes a support-magnetic head assembly in which the head abuts the bottom of a housing.
This invention aims to improve the resistance of the head (or heads) in its (their) support.
To this end, the invention proposes a chip(s)-base assembly characterised in that it includes a base and a cover over at least part of the chip(s), the chip(s) being embedded in a housing between the base and the cover. This embedded housing can be located either completely within the base, or completely within the cover, or partially within the base and partially within the cover.
In the case of a single chip, the chip having two lateral sides, an upper side, a lower side and a rear side, at least one of these sides can be glued to the wall of the embedded housing. At least two sides can possibly be glued. The lower side of the chip can also be glued to the bottom of the housing, keeping in mind that, without particular precautions, the thickness of the glue could affect the positioning of the chip. Thus glued and embedded, the chip is held solidly on the base.
The chip can also, in certain cases, be glued to the cover. This cover can be a hollow piece fitting against the base.
The chip can include one or several magnetic heads. There can also be several chips on the base, each embedded in a housing (or in the same housing), ensuring its relative positioning with respect to the others both laterally and in terms of depth.